the rays from the other 

 half and reflects them 

 into the oblique tube. 

 The result is an image in 

 each eyepiece, thus giv- 

 ing stereoscopic vision. 

 This gives a perception 

 of depth, a sense of 

 being able to look into 

 an object, and conveys 

 to the mind the im- 

 pression of roundness 

 or separate appreciation 

 of the different planes 

 of the object which it 

 is impossible to obtain 

 with monocular vision. 

 Its use, however, is 

 limited to the lower 

 power objectives. 



Coarse Adjust- 

 ment. In providing 

 this adjustment, two 

 methods are followed. 

 The most simple form is 

 the sliding tube in which 

 the body tube, which 

 carries the nose-piece at 

 the lower end and draw- 



Fig. 30. 



45 



